Probably music's angriest old man, Baker gives the American journalist and film-maker Jay Bulger pure film gold – that Bulger uses at the beginning and end of his documentary – by getting furious on discovering that people other than him were to be interviewed, and actually whacking Bulger in the face with his cane. Thank heaven the director didn't raise that other very English subject with him: anti-ginger prejudice. He could have found himself being buried in some corner of the gated South African compound where Baker now lives with his fourth wife, and where Bulger correctly notes that the country's laws are unenforceable.

Baker was the brutally brilliant drummer who became the percussive wild man with Cream, alongside Eric Clapton and Jack Bruce, and other bands such as Blind Faith. He also has a genuine claim to be the first western musician to investigate and popularise African music, setting up a short-lived recording studio in Lagos, Nigeria, in the early 1970s, making music with Fela Kuti – and bizarrely acquiring a rich man's taste for polo. He was apparently cheerfully indifferent to that city's scary reputation, until he was effectively chased out of the country by some heavy characters. After stints in Italy and the United States, the expatriate Baker has wound up in South Africa, where he has blown all the cash he got for the 2005 Albert Hall Cream reunion on a string of polo ponies, and grumpily complains that he is now "broke". Sitting plumply in a recliner, Baker gives Bulger his audience, cross and obnoxious throughout, often denouncing his interviewer as a "dickhead", and wearing dark glasses. Some earlier interview footage shows Baker with a faster, lighter voice. Now it has slowed and deepened into a resentful groan.

Baker grew up during the second world war, and took to heart a letter left for him when he was 14 by his late father: "Use your fists; they are your best pals." This he did, but Bulger's film shows how his aggression was poured out on to the drumkit, tempered with talent and a sense of what Baker gnomically calls not rhythm but "time".

Baker became acquainted with the soon-to-be-big names in the 1960s, but becomes noticeably nettled when Bulger asks about them. The thought of "effeminate" Mick Jagger makes him seethe. "I thought, 'Who is this stupid little cunt?' I terrified the shit out of him." Later, he would punch Cream bassist Bruce, on stage, out of pure, fanatical dislike.

The film's best moment is something that goes beyond anything in This Is Spinal Tap. When poor Steve Winwood was forming the band that was to become Blind Faith, Ginger simply showed up uninvited at the first meeting, and asked when they were starting. Out of embarrassment and fear, they had to let Ginger be the drummer. He rattled on from band to band, indulging in hookers and groupies on the road, and leaving wife and children behind to deal with heartbreak and bankruptcy.

Bulger has access to a treasure trove of black-and-white photographs, which he digitally tweaks and manipulates. He interviews plenty of other musicians (that sore point) including a comfily cardiganed Clapton. Everyone is pretty clear that Baker is way better as a drummer than men such as John Bonham and Keith Moon. But the star interviewee Baker is, to quote Andrew O'Hagan's phrase, "as English as two weeks in Essex". In his sunbaked, ill-tempered exile, he looks like a forgotten member of the Great Train Robbers, or a lost Piranha brother, with a touch of Wilfrid Brambell. Also, as an intense younger man, Baker had a touch of Will Self.

No one said he had to be nice. He's not. And there's no heartwarming reconciliation on the cards between Baker and his grownup son, who is also a drummer. But when we are always being told that books and movies have to have "sympathetic" lead characters – well, here's a documentary that does very well without one.